Dust separator



March 28, 1939. H. VAN TONGEREN 2,152,114

DUST SEPARA'IOR 4 Sheets-Sheet 1 Original Filed Aug. 11, 1952 March-28,1939. 1 H. VAN TQGEREN 2.152.114

DUST SEPARATOR Original Filed Aug. 11, 1952 4 Sheets-Sheet 2 March 28,1939.

Original Filed Aug. 11, 1932 un m H. VAN TONGEREN DUST SEPARATOR 4Sheets-Sheet 5 F f '.i

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March 28,1939. H. VAN TONGEREN DUST SEPARATOR Original Filed Aug. 11,1932 4 Sheets-Sheet 4 Patented Mar. 28, 1939 DUST SEPARATbB Hermannusvan l'ongeren, Heemstede,

Netherlands Original application August 11, 1932, Serial No.

1936, Serial No. 72,400.

August 17, 1931 Divided and this application April 2,

In the Netherlands 10 Claims. (Cl. 183-83) This invention relates toapparatus for removing dust and other foreign matter from air, fluegases and the like, and has particular reference to apparatus for thispurpose as disclosed in my prior application, Serial No. 628,408, filedAugust 11, 1932, now Patent No. 2,039,692, of

- which the present application is a division.

As explained in my aforesaid patent when a. current of air or gas isrequired to follow a curved 10 path, there is set up what is known as adouble eddy current; that is, secondary air or gas currents flowinglaterally outward from the middle of the main air or gas current.

Generally speaking, the object of the present 15 invention is the sameas set forth in my aforesaid prior patent; viz., to provide apparatusfor utilizing the double eddy current set up by a current of air or gastraveling a curved path, to assist in removing dust and other foreignmatter 20 from the air or gas.

More particularly, the present application is directed to apparatus asillustrated and described in my aforesaid application, but notspecifically illustrated, described nor claimed in my aforesaid patent,and in this connection a more specific object of the present inventionis to provide, in dust removing apparatus of the cyclone type, novel andpractical means for utilization of the double eddy current existent insuch ap- 30 paratus as a material aid in the rapid and emcient removalof dust and other foreign matter from air or gas passing through theapparatus.

With the foregoing and other objects in view, which will become morefully apparent as the 5 nature of the invention is better understood,the

same consists in dust removing apparatus embodying the novel features ofconstruction, combination and arrangement of parts, as will behereinafter more fully described, illustrated in 40 the accompanyingdrawings and defined in the appended claims.

In the drawings:

Figure 1 is a vertical section through a dust removing apparatus of thecyclone type con- 45 structed in accordance with one practicalembodiment of the invention, the section being taken on the line |-l ofthe cross sectional view,

Figure 3.

Figure 2 is a side elevation of the apparatus 50 shown in Figure 1.

Figure 3 is a cross section on the line 3-3 of Figure 1.

Figures 4, 5, 6 and '7 are detail cross sections on the lines 4-4, 5-5,6+6 and 'I-1, respec- 65 tively, of Figure 1.

Figure 8 is a side elevation of a dust removing apparatus of the cyclonetype constructed in accordance with an alternative embodiment of theinvention.

Figure 9 is a vertical section through the ap- 6 paratus shown in Figure8.

Figure 10 is a cross section on the line Ill-l0 of Figure 8.

Figure 11 is a cross section on the line Il-ll of Figure 9. 10

Figures 12 and 13 are views similar to Figure 1 illustrating otheralternative embodiments of the invention.

Figure 14 is a view similar to Figure 1 illustrating still anotheralternative embodiment of 15 the invention.

Figure 15 is a. cross section on the line l5- l5 of Figure 14.

Figure 15a is a cross section on the line Ilia-45a of Fig- 15.

Figure 16 is a graph illustrating relative efflciencies of apparatusconstructed in accordance with the invention (solid line) and apparatusconstructed in accordance with prior practice (dotted line) withreference to different positions of the air or gas outlet of theapparatus; and

Figure 17 is another graph illustrating relative efficiencies ofapparatus constructed in accordance with the invention (solid line) andapparatus constructed in accordance with prior practice (dotted line)with reference to dust loading of the air or gas.

Referring to the drawings in detail, first with particular reference tothe embodiment of the invention illustrated in Figures 1 to 7, it willbe observed that the apparatus is of the cyclone type and includes acasing A the top portion III of which is of convolute form havingvertical walls and is closed at its top by a top wall 46 having formedcentrally therein an opening through which an air or gas outlet pipe 32extends a suitable distance downwardly into the portion l0, preferablyto a point below the middle of said portion.

From its top portion ill the casing A tapers downwardly, as indicated atH, to the top of a portion 43 which may be either of convolute orcylindrical form, and from the bottom of said portion ll said casingagain tapers downwardly, as indicated at l2, to its dust outlet, openlower end 35 of relatively small diameter.

Opening tangentially into the top portion I0 is an air or gas inlet cond't 28 of any suitable width and height which essentially has its topdisposed below-the top wall 46 of said casing as portion ill and abovethe lower, open end d0 of the outlet pipe 32, and which preferably is ofsuch height that its lower end is disposed below the lower, open end,ill! of. said outlet pipe 32 and near the bottom of said portion Ill,the said lower, open end ll] of the outlet pipe 32 preferablybeingdisposed approximately midway between the top and the bottom ofsaid inlet conduit 28.

At a point approximately diametrically oppo site the inlet conduit 28the top portion In of the casing A is formed to provide a skimmingopening 37 facing counter to the direction of flow of air or gas in a.curved path; as indicated by the arrows at in Figure 3, from the inletconduit 28 through the portion In, and, as shown, the top of saidskimming opening is disposed at the extreme top of said portion 10, saidopening being of any suitable height and preferably of such height thatits lower end is disposed in a plane only slightly below the plane ofthe In preferably vertical alinement with the skimming opening 31 thecasing portion H is formed to provide a second skimming opening 44 whichfaces in the same direction as the opening 31 and which may be of anysuitable height, its top pref erably being disposed at the top of saidcasing portion Ii.

The skimming openings 31 and as open into a duct which extendsdownwardly to a side opening 62 in the casing portion 43 where vanes l3,disposed as shown in Figure 7, preferably are provided to deflect theair or gas, travelling around the casing in the direction of theaforementioned arrows a, across said opening 42.

Where the inlet conduit 28 enters the casing there preferably isprovided a vane 50 which is adjustable to vary the efiective width ofsaid inlet conduit.

Air or gas entering the portion 1 t of the casing A through the inletconduit 28 flows in a primary curved path following the curvature of theportion it as indicated by the arrows a and thereby sets up what isknownas the aforementioned double eddy current. In other words, theprimary current divides medially into a pair of secondary currents oneof which flows upwardly and outwardly and the other of which flowsdownwardly and outwardly. The primary air or gas current carries dust orother foreign matter suspended in the air or gas, toward the peripheryof the casing, and the secondary air or gas currents carry the dust orother foreign matter upwardly and downwardly, respectively. The skimmingopenings 37 and M are located where the dust or other foreign matterwouldin the absence of said openings and due to the combined action ofsaid primary and secondary currents, tend to concentrate at the upperouter comer of the casing portion l0 and at the junction of the casingportions I 0 and H. Consequently, there results a highly efiicient andrapid removal of with some of the air or gas being carried downwardlythrough the duct 36 again into the casing A at a point in the lowerportion of said casing where the air or gas, due to its cyclonic flowtoward the outlet pipe 32, as illustrated by the arrows in Figure 9,sweeps the top of the inlet conduit 28.

thereby to enable arcane wardly with the outer fringe of the cyclonicflow and finally mixes with the upwardly traveling vortex of said flow,so that it again is subjected to cleaning when it enters the uppercasing portion Hi. However, instead of having the lower end of the duct36 connected with the casing A, the said lower end of said duct may beconnected directly with a dust receptacle.

By having the lower, open end of the outlet pipe 32 disposed in a planeapproximately midway between the top and the bottom of the inlet conduit28, that is, in the plane of division between the secondary air or gascurrents, any direct flow of air or gas from the conduit 28 to the pipe32 is avoided and, therefore, all of the air or gas entering the casingthrough the conduit 28 is subjected to cleaning by the skimming openings37 and it before it eventually becomes part of the cyclonic flow towardand through said outlet pipe 32.

more elongated vertically; the

nected with the casing portion l0 in the plane of the lower, secondaryair current. By this construction the top strata of the air or gascomprised by the upper, secondary air current is cleaned by the skimmingopening 31 as in the case of the Figure 1 construction, while the lower,secondary air current by sweeping downwardly across the opening 42 bywhich the duct 36 is connected with the casing portion I0 assists insweeping dust entering the casing through said opening, downwardly intothe bottom of the casing for discharge through the lower, open endthereof. At the same time, the lower strata of the incoming air or gascomprised by the lower, secondary current, is cleaned by the cyclonicflow of the air or gas in the lower part of the casing. Figures 8 to 11additionally illustrate that the skimming opening 31 is disposed at thesame side of the casing as the air or gas inlet conduit 28, so that airor gas entering the casing through said inlet conduit flowssubstantially entirely around the casing before it is skimmed of dust bythe opening 31 obviously the Figure 1 construction may be modified inrespect to the disposition of its skimming openings in accordance withthe illustration of Figures 8 to 11.

Figure 12 of the drawings illustrates an embodiment of the inventionwhich is essentially the same in construction and mode of operation asthe embodiment of the invention illustrated in Figures 8 to 11, exceptthat the inlet conduit 28 is of lesser height and the skimming opening31 is elongated circumferentially of the-casing, a greater amount of theupper, secondary air current to pass into the duct 36'.

the duct 36 part of the struction, instead or with the top portion ofthe casing 'as in the Figures 8 to 11 construction. In

accordance with the disposition of the opening 42 of the Figure 13construction, the inlet conduit 26 and the lower end of the outlet pipe32 are lowered-as compared with the Figures 1 to 7 and the Figures 8 to11 constructions.

The dust collecting efflclency of a cyclone is a function of the depth Zof the outlet-pipe 32 in the body of the cyclone (see Fig. 12). In thediagram of Fig. 16 the efficiency n is plotted against the quotient l/h,where l=the depth of the outlet pipe and h=the height of the cylindricalpart of the cyclone (see Fig. 12). Line A-- B-C shows the emciency-of ausual type of cyclone without dust-circulating pipe 36. It will be seenthat theefllciency is maximum when the outlet-pipe 32 is introduced verydeeply so that l is about as long as h (point B in the diagram).

When the outlet-pipe ls raised,the efllciency constantly decreases (BA).It is an error to explain this by'the lack of time for the dustparticles to reach the periphery; it is entirely due tothe unsuitableconstruction of the usual type of cyclone by ignoring the influence ofthe doubleeddy current.

This is proven by the effect of the simple dust by-pass pipe 36, withoutany other alteration in this usua type of cyclone. If one provides theby-pass 36, the efllciency depends also upon the depth of theoutlet-pipe 1 into the cyclone body, as shown in the line DE-F in thediagram, Fig. 1'7. Now the maximum is somewhat deeper than the half ofthe height of the cylindrical part, being just the place where the twohalves of the double-eddy current border upon each other. This meetingpoint of the two halves of the double-eddy current will be foundsubstantially to lie in the plane dividing the cyclone in two equalhalves by volume. There is nothing altered in the pathof the gases, sothat the gain in efliciency 'I-K is due solely to the carrying away ofthe dust-ring, which, in the absence of the skimming opening 31, wouldform at the upper, outer corner of the cyclone.

As the line DEF is nearly symmetrical and D is nearly as low as F thereis no evidence'of the influence of a long path and a long time for theseparation. The loading of the gases is minimum where the two halves ofthe eddy current border upon each other, and this is therefore the mostsuitable place for the outlet 40.

The provision of the dust by-pass 36 has been shown to have a furtherimportant influence on the behaviour of the cyclone. In the hithertousual construction, increase in dust-loading of the gas increases thecollection efliciency (see curve A-B-C, Fig. 17, where efllciency n isplotted against the loading of .the gases in grams.

per cubic meter). In a cyclone constructed according to the presentinvention the efficiency increases with reduction in dust-loading and isat its highest when the dust-loadingis lowest with the dust by-pass inration (see curve Diagram 1'7 of which portio E-F relates to the cyclonewhen fitted with by-ffis sli A further feature of importance in designfor securing high efllciency relates to the position of the inlet to thecyclone.

By lowering this so that it approximates as nearly as may be to themiddle region of the cyclone the efliciency is increased, by reason ofthe fact that at this point the forces of the double-eddy current andcentrifugal action are in cooperation as also that the introduction ofthe dust-laden'gas at the region of dust concentratiorr 29 is therebyavoidedwm The advantages of the dust by-pass pipe 36 are: (1) higherefllciency, (2) less wear at the top of the cyclone, (3) the dust isdischarged constantly and not intermittently.

Although only a single dust by-pass pipe 36 as shown gives a great gainin efficiency, two or more such pipes may be provided on each cyclone.Such external pipe or pipes 36 may also be replaced by a concentricplate 36d around and slidably spacedfrom the cyclone casing and providedat its top with a plurality of skimming openings 31d and at its bottomwith an annular 15 slot 42d in which is an annular series of vanes l3d.

. The influence of the double-eddy current on functions and design ofthe upper part of the usual cyclone having been pointed out, importantfeatures in the lower part of the cyclone may now 9 be set out accordingto the invention.

In Fig. 9 is shown what happens in the lower part of a cyclone. Thecurrent 49 carries the separated dust towards the bottom and dust-outlet35, but in the centre the gases rise and form a windspout or vortex 39.By the currents 'I a part of the separated dust is brought ,to the footof the vortex and this dust is sucked into the swirling central columnof the spiral vortex 38 and conveyed to the top 40. The result is that apart of this dust is lost and escapes through the outlet-pipe 32.

This is a very important cause of inefllciency in the usual types ofcyclones. The vortex 39 is also responsible for the fact that ordinarycyclones have a maximum efllciency at a certain moderateentrance-velocity of the gas, whilst increasing the velocity of entrancebeyond this point decreases the efliciency.

The explanation is to be found in the fact that 40 in the usual types ofcyclone the dust forms not only rings at the top of the cyclone, butalso in the lower conical part near the discharge 35. Here thecentrifugal force tends to remove the dust from the centre, but thebranch 49 of the double-eddy current tends to bring the dust to thedischarge 35. Therefore at several points of the conical part 34 certainfractions of the dust are in equilibrium and turning round the axis,without being discharged. They may make hun- 50 dreds of revolutionsbefore accidently reaching the .discharge 35, and during all that timethe finer dust particles are carried along with the current 49, broughtto the foot of the vortex, and conveyed to the outlet 40.

It is not possible to avoid the vortex 39 but it is possible to avoidthe formation of the-dustrings near the discharge 35 and to limit thedustentraining action of the vortex.

Fig. 13 shows the manner in which this may be secured. The conical partof the cyclone must be elongated. This has a double effect. The upwardcomponent of the resolved centrifugal force is reduced whilst at thesame time the inward tendency of the current 1 is correspondinglyweakened so that dust will be less easily carried towards the risingcolumn of the vortex. The cone ll" of Fig. 13 will give a higherefficiency to the cyclonethan the cone 34 of Fig. 12.

The dust by-pass pipe 36 is extended to the lower region in the cone andreintroduces the dust at 42. In Figure 13 is shown an improved type ofcyclone with main inlet 28 near the midpoint between the two halves oftheeddy current, and removed from the region immediately under 76 thetop cover of the cyclone with the outlet 40 at substantially the samelevel, and with a dustcirculating pipe 36 and elongated cone 4".

For highest efficiencies the cone of the cyclone must be an extended onewith a small angle or the lower portion of the cyclone must compriseconical rings of decreasing angle at L (Fig. 1) or alternate cones andcylinders.

The ideal profile for the cone is H--IJKL in Fig. 1, but practically thesame effect may be obtained by replacing this curve by composite conesand cylinders. The cylindrical part at in Fig. 1, or a similar cylinderlower down, is conveniently utilized to re-introduce the by-pass pipe 36into the cyclone. However as previously stated this by-pass may withequal advantage deliver into a chamber below outlet 35.

The slot M (Fig. 1) is not always necessary. In general there will beprovided dust-evacuation or skimming devices along the pipe 36 at placesin the cyclone where the dust tends to form rings. Just as the dust ringat the top of the cyclone is taken away by the skimming place 31, so atany other place where the dust tends to assemble it may be evacuated bya slot. In this manner also the cyclone is immediately clean when nofurther dust is introduced, whereas the usual type of cyclone does notclean itself.

The cyclone shown in Figs. 1 and 13 has its maximum of efficiency not atlow but at higher velocities. However even at low velocity the chiciencyis much higher than of the type shown in Fig. 12.

The essential characteristics of a cyclone, according to the invention,are: gas inlet and outlet substantially at the junction of the twohalves of the double-eddycurrent, an external dust bypass pipe 36 and anelongated cone 55, or cones in combination with a cylinder @3.

What I claim is:

1. Apparatus for removing dust and other foreign matter from a gascomprising a vertically disposed casing the upper portion of which has acurved, substantially vertically disposed side wall, a wall closing thetop of said casing, said casing having a gas inlet opening, a gas supplyconduit disposed to discharge tangentially into said casing through saidinlet opening, a gas outlet pipe extending through the top wall of saidcasing downwardly into said casing and having its lower end open anddisposed between the planes of the upper and the lower ends of saidinlet opening, the side wall of the casing having a tangentiallydisposed skimming opening extending upwardly to the top wall of saidcasing, and a dust discharge duct leading from said skimming opening.

2. Apparatus as set forth in claim 1, in which the dust discharge ducthas a dust outlet in the wall of the casing, said outlet being situatedbelow the open lower end of the gas outlet pipe.

3. Apparatus as set forth in claim 1, in which the casing has a secondtangentially disposed skimming opening located at a level below the openlower end of the gas outlet pipe and communicating with the dustdischarge duct.

4. Apparatus as set forth in claim 1, in which the wall of the casinghas a plurality of tangentially disposed skimming openings extendingupwardly to the top wall of said casing, and circumferentially spacedapart, and in which a jacket is disposed around and spaced from the topportion of the casing to provide the dust discharge 1 duct.

5. Apparatus as set forth in claim 1, in which the lower, substantiallyconical portion of the easing comprises an upper and a lowersubstantially conical section interconnected by a substantiallycylindrical section, and in which the duct leading from the skimmingopening downward discharges through an opening in the wall of saidsubstantially cylindrical section.

6. Apparatus as set forth in claim 1, in which the lower, substantiallyconical portion of the casing comprises upper and lower substantiallyconical sections and a substantially cylindrical section connecting thesame, in which the dust discharge duct leads downwardly from theskimming opening and-is in communication with the casing through anopening in said substantially cylindrical section, and in which thecasing has an additional tangentially disposed skimming opening locatedat a level below the open lower end of the gas outlet pipe andcommunicating with said dust discharge duct.

7. Apparatus for removing dust and other foreign matter from a gascomprising a vertically disposed casing the upper portion of which hasa. curved substantially vertically disposed side wall, a wall closingthe top of said casing, the lower portion of saidcasing being ofsubstantially conical form, a gas inlet conduit communicatingtangentially with said casing, a gas outlet pipe extending through thetop wall of said casing downwardly into said casing and having an openlower end disposed between the planes of the upper and the lower ends ofthe inlet conduit, the side wall of the casinghaving a tangentiallydisposed skimming opening extending upwardly to the top wall of saidcasing, the lower, conical portion of said casing having a tangentiallydisposed skimming opening, and a duct leading from said first mentionedskimming opening to said second mentioned skimming opening.

8. Apparatus as setforth in claim 7 in which the lower, substantiallyconical portion of the casing comprises upper and lower substantiallyconical sections and a substantially cylindrical sectioninterconnectingthe same, and in which the duct leads downwardly from the skimmingopenings and is in communication with the casing through an opening insaid substantially cylindrical section.

9. Apparatus as set forth in claim 7 in which the skimming openings aredisposed, one above and the other below the horizontal medial plane ofthe air' or gas inlet opening.

10. Apparatus as set forth in claim 7 in which the top of the air or gasinlet conduit is disposed below the top of the casing and above thelower open end of the air or gas outlet pipe.

HER S van TONGEREN.

